X-ray tube



I June 14,1927.

G. HOLST ET AL X-RAY TUBE Filed Jan. 15, 1925 ww 7% W W wW Patented June 14,1927o .s'r'rss rATENT OFFICE.

'I.@ It, V. PHILIPSVG'EQEILAMPENFABRIEKEN, 01E EINDHOVEN, NETHERLANDE.

x-r TUBE.

Application flier! Yanaary 15, 1828, serial No. 2,559, and in the Netherlands March ll), 1924:.

The present invention relates to X-ray tubes with an incandescent cathode.

In order to obtainvthat the cathode rays will strike the anti-cathode ,on a limited 5 surface, the so-called focus, the known Coolidge-X-ray tubes have hitherto been provided with a focussingdevice which assembled the cathode-rays to a concentrated beam already in the neighborhood of the cathode. m In this case the incandescent cathode is arranged in concentrated form, for example in the shape of a spiral, within acylindrical focussing device.

According to the invention, the incandes- 15 cent cathode is arranged within a metal, vessel extending inside the outer wall of the tube, the anti-cathode being so insulated from the said vessel that this insulation is capable of resisting the operating voltage to W be supplied between the incandescent cathode and theanti-cathode. On the side of the anti-cathode the metal vessel is constricted to form an opening for the passage of the cathode-rays, and that part of the anti-' cathode on which the cathode-rays strike, is arranged in or near that opening.

The metal vessel may be so constructed as. to surround the incandescent cathode almost entirely. It is obvious that apart from w the aperture for the passage of the cathoderays an opening in the vessel must be proyided for letting through the X-rays, which opening, however, if desired, may be shut ofl by means of a metal window or gauze 35 which allows the X-rays to pass.

7 As the anti-cathode is arranged in the neighborhood of the opening of the metal vessel a considerable part of the X-rays take their way through the metal vessel, another 0 part being, absorbed at any rate partly,

by the walls of the said vessel.

g In operating the X-ray tube according to the invention, the metal vesselwithin which the incandescent cathode is arranged, is con 5 nected to the incandescent cathode, either The fact that the incandescent cathode for the greater part is enclosed by a metal vessel having a constant, preferably, a negative p tential, ofiers the advantage that the X- ray tube operates constantly, the irregular charging of a glass wallcausing no longer any trouble.

Another advantage is that the X-ra ye emanate merely from the anti-cathode mir ror, not from other parts of the anti-cathode.

in X-ray tubes according to the invention the cathode-rays are concentrated on a limited area of the anti-cathode owing to the peculiar shape and the arrangementof the metal vessel and the anti-cathode relatively to each other.

it is no longer necessary to arrange the incandescent cathode in a concentrated sha e whilst a focussing device which encloses t c incandescent cathode more or less tightly, may likewise be omitted, 1

By a proper choice of the shape and the arrangement of the metal vessel and the anti-cathode relatively to each other, care can further be taken that the active X-rays leave the surface of the anti-cathode at right angles or substantially right angles thereto, which involves the advantage that unevennesses on the surface of the anti-cathode give less occasion to absorption of the X- rays.

As in X-ray tubes according to the inve t on it is no longer necessary to give a concentrated form to the incandescent cathode, 1t becomes possible accbrding to the invention to coaxially arrange the part of the anti-cathode struck by the cathode-rays, the

opening'in the metal vessel for the passa e of the cathode-rays and the aperture or t e Window for letting through the X rays.

The accompanying: drawing illustrates by way of example a construction of an X-ra tube according to the invention.

In the drawing representing a longitudinal section of the X-ray tube, the outer wall of the X-ray tube is constituted by a glass vessel 1 to which a re-entrant glass tube 2 is hermetically sealed. An anticathode dconsisting, for example, materially of chrome-iron is hermetically sealed to the end of the tube 2. An insertion piece 4 consisting, for example, of tungsten, is secured to the front face of the incandescent cathode and a metal tube 5 serves to supply a coolby a straight wire made for example of tungsten, is secured within the metal vessel 9 to leading-in wires 11 andul2 which are hermetically sealed into the wall of the vessel 1 and which. are insulated from the metal vessel 9 by means of quartz beads 13 and 14.

. On the side of the anti-cathode the me tal vessel 9 is constricted to an opening 15 and on the other side an aperture or window 16 is provided in order to allow the X-rays to pass. I

When 0 crating the tube a high tension is supplie between the incandescent cathode 10 and the.anti-cathode 3 and a potential being preferablyslightly negative relatively to all points of the filament, is given to the .vessel 9 to which a-leading-in wire 17 is connected. The electrons emitted by the filament, are not capable of reaching the metal vessel 9 but owipg' to'the peculiar shape of the metal vessel and to the arrangement of the anti-cathode they are forced to strike the front-face of the anti-cathode on a limited area. It will be observed that the active X-rays leavethe surface of theanticathode in a perpendicular"- or almost perpendicular direction.

' X-ray tubes according to the invention may be exhausted in some'known manner so that the discharge occurs practically without aeaaaae any gas-ionization. The tubes may likewise be provided with a gaseous filling con-' sisting of hydrogen or helium which has such a pressure that no detrimental gasionization occurs. This gas pressure may be above 0.0006 millimetre of mercury and in case of a hydrogenous filling it ma amount, for example, to about 0.01 millimetre.

What we claimus: 1. An X-ray tube comprising an incandescent cathode characterizedin that vthe in- 'cande'scent cathode is arranged within a metal vessel extending inside the outer wall of the tube, the anticat-hode being so insulated from the said vessel that this insulation is capable of resisting the operating voltage to be supplied between the incandescent cathode and the anticathode, the-said vessel atthe'side of the anticathode being constricted to form an opening for the passage of the cathode rays, the part of the anticathode which is struck by the cathode rays being located near said vessel. 0

2. A11 X-ray tube comprising an incande's cent cathode, characterized in that the incandescent cathode is arranged, within a metal vessel extending inside the outer wall of the tube, the anticathode being so insulated from the said vessel that this insulation is capable of resisting the operating voltage to be. supplied between the incandescentcathode and the anticat-hode a part of said metal vessel being arranged closely tothe anticathode and being so constructed in. relation to said anticathode thatthe cathode rays are assembled and are located on a small part of the anticathodea y In testimony whereof we afiix our signatures, at the city of Eindhoven, this 22nd day of December, A. D. 1924.

GILLES. HOILST. ALBERT BOUWERS. 

